Qucosa – Hemholtz-Zentrum Dresden-Rossendorf
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Bestimmung der Aufbruchtemperatur hochangeregter Kerne aus Isotopenverhältnissen leichter Fragmente
Get PDFThermal dilepton and open charm signals versus hard initial yields in heavy-ion collisions at RHIC and LHC energies
Get PDFThe hard initial production of open charm and dileptons is compared with possible thermal signals in heavy-ion collisions at RHIC and LHC energies. Our approach is based on the perturbative QCD mini-jet mechanism of quark-gluon matter formation. The thermal dilepton signal is found to rise much stronger as compared to the hard Drell - Yan background with increasing collider energy and clearly dominates at LHC energy. Oppositely, open charm stems from initial hard production. A possible rnanifestation of gluon shadowing at RHIC and LHC energies is discussed
Solare Warmwasserbereitung und Fernwärmeeinspeisung -Waldblickschule Freital-
Get PDFIn ein mit Erdgas betriebenes konventionelles Fernwärmesystem (Anschlußleistung 2,1 MW) wurde eine Solarkollektoranlage mit einer Bruttofläche von 100 m² integriert. Die Kollektoranlage diente vorrangig der Erzeugung von Brauchwarmwasser für eine Schule, solare Überschüsse wurden in den Rücklauf des Fernwärmesystems eingespeist. Ein umfangreiches Meßprogramm ermöglichte Effizienzuntersuchungen des Systems. Der jährliche Nettoertrag des Solarsystems lag bei 280 kWh/m² bei einem Systemnutzungsgrad von 26%. Beide Kennziffern wurden durch hohe Rücklauftemperaturen (58°C) im Nahwärmenetz negativ beeinflußt. Weitere Untersuchungen galten dem Betrieb der eingesetzten Schichtspeicher (Reihenschaltung). Bei Ausschöpfung der in dem Vorhaben deutlich gewordenen Optimierungspotentiale können in künftigen Anlagen Nettoerträge von 350 kWh/m² und solare Wärmegestehungskosten unter 30 Pf./kWh erreicht werden
Relativistic Description of Exclusive Deuteron Break-up Reactions
Get PDFThe exclusive deuteron break-up reaction is analyzed within a covariant approach based on the Bethe-Salpeter equation with realistic meson-exchange interaction. Relativistic effects in the cross section, tensor analyzing power and polarization transfer are investigated in explicit form. Results of numerical calculations are presented for kinematical conditions in forthcoming p + D reactions at COSY
Diphoton rates from thermalized matter resulting in ultra-relativistic heavy-ion collisions
Get PDFDiphoton radiation off strongly interacting matter resulting from ultrarelativistic heavy-ion collisions is estimated for SPS and RHIC conditions. At SPS emrgies tha thermal diphoton signal competes strongly with the Drell - Yan like background. For given charged-particle rapidity density a scenario with deconfinement transition predicts a larger diphoton yield than a scenario without phase transition. For RHIC energies we find that radiation from initially undersaturated (but gluon-rich) deconfined matter overwhelms the hadron gas and the Drell - Yan like diphotons in the invariant mass window 1 < M < 2.5 GeW. Due to this the so-called M1 scaling is approximately obtained and can serve as additional tsol for discriminating radiation from quark-gluon matter
Decay rates of resonance states at high level density
Get PDFThe time dependent Schrödinger equation of an open quantum mechanical system is solved by using the stationary bi-orthogonal eigenfunctions of the non-Hermitean time independent Hamilton operator. We calculate the decay rates at low and high level density in two different formalism. The rates are, generally, time dependent and oscillate around an average value due to the non-orthogonality of the wavefunctions. The decay law is studied disregarding the oscillations. In the one-channel case, it is proportional to t-b with b ≈ 3/2 in all cases considered, including the critical region of overlapping where the non-orthogonality of the wavefunctions is large. Starting from the shell model, we get b ≈ 2 for 2 and 4 Open decay channels and all coupling strengths to the continuum. When the closed system is described by a random matrix, b ≈ 1 + K/2 for K = 2 and 4 channels. This law holds in a limited time interval. The distribution of the widths is different in the two models when more than one channel are open. This leads to the different exponents b in the power law. Our calculations are performed with 190 and 130 states, respectively, most of them in the critical region. The theoretical results should be proven experimentally by measuring the time behaviour of de-excitation of a realistic quantum system
Application of the Guiding Centre Approximation to the Transport of Injected Fast Ions in a Mirror Based Plasma Neutron Source
Get PDFThe guiding centre appraximation for the motion of charged particles in axially symmetric magnetic and electric fields is formulated and stopping as well as small angle scattering on a multicompenent plasma are included. The developed code has been applied to the design of a 14-MeV neutron source according to the concept of the Budker Institute Novosibirsk. It is demonstrated that the self-interaction of injected D and T ions by stopping, scattering and induced internal Fields has to be taken into account, if the injected power exceeds a few megawatt
Interfering Doorway States and Giant Resonances II: Transition strengths Manuskript-Nr.: CC6302
Get PDFThe mixing of the doorway components of a giant resonance due to the interaction via the common decay channels influences significantly the distribution of the multipole strength and the energy spectrum of the decay products of the giant resonance. The photoemission turns out to be most sensitive to the overlapping of the doorway states. At high excitation energies, the interference between the doorway states leads to a restructuring towards lower energies and apparent quenching of the dipole strength